Author: Assoc Prof Patrick Emanuel, Dermatopathologist, Auckland, New Zealand, 2013.
Toxoplasma gondii is often a life-threatening infection in immunesuppressed patients. Frequently, infection does not represent a primary infection with the organism, but rather, is a reactivation of a previously silent or suppressed infection. Most cases of reactivation involve the central nervous system; however, lung and skin involvement have been reported.
Toxoplasma gondii bradyzoites and tachyzoites may be identified within the epidermal keratinocytes (figure 1, arrow). The associated reaction pattern can mimic an interface dermatitis.
The bradyzoites and tachyzoites of Toxoplasma gondii are quite characteristic. A specific immunohistochemical stain is available. Correlation with serologic studies can also be helpful.
Normal skin – The causative organisms can be easily overlooked.
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